Ok, I've seen pics of SOHC stang engines where the timing chain is right in the middle with the cam shaft on top and the crank shaft in the bottom and obviously connected by the timing chain and gears....but I want to know how the timing chain moves these gears to spin the crank/cam to work in relation, basically how do they work together/purpose??? Thanks.

 

Think of the chain as the same thing as the serentine belt on the front of the engine because it is the same thing.The only difference is the chain can't slip on the gears.The timing gears turn the same direction as the crankshaft when using a chain.If you put two gears together one gear turns one way and the other turns the opposite direction.Three gears put the two outside gears spinning the same direction.If you tried to use a gear train to turn the cams in a modular engine there would be so many gears that the timing would never even be close to optimum.Single OverHead Cam(SOHC) engines can be made to rev higher because of less valve train inertia than an engine with a single camshaft.Also valve train dynamics such as pushrod flex and spring bounce can be more carefully controlled because there are no pushrods to flex.The springs can be made lighter because they have less weight to control,they only have to pull the valve shut and keep the rocker arm against the cam lobe.The cam chains self adjust,and in this way keep the timing of the cams within tolerances for a considerable amount of time.The pushrod camshafts have no tensioners and as the gears wear and the chain stretches,valve timing and spark timing accuracy falls off.There are kits to change from chains to a gear set in the pushrod engines and they seem to work well but make a bit more noise than the original chain drive.Hope this helps.